Dry eye, also known generically as keratoconjunctivitis sicca, is an ocular surface disease characterized by tear film compositional/rheological abnormalities and excessive inflammation that leads to dysregulation of the corneal and conjunctival epithelial cell barrier function. It is a common opthalmological disorder affecting millions of Americans each year. The condition is particularly widespread among post-menopausal women due to hormonal changes following the cessation of fertility. Dry eye may afflict an individual with varying severity. In mild cases, a patient may experience burning, a feeling of dryness, and persistent irritation such as is often caused by small bodies lodging between the eye lid and the eye surface. In severe cases, vision may be substantially impaired. Other diseases, such as Sjogren's disease and cicatricial pemphigoid manifest dry eye complications.
Although it appears that dry eye may result from a number of unrelated pathogenic causes, all presentations of the complication share a common effect, that is the breakdown of the pre-ocular tear film, which results in dehydration of the exposed outer surface and many of the symptoms outlined above (Lemp, Report of the National Eye Institute/Industry Workshop on Clinical Trials in Dry Eyes, The CLAO Journal, volume 21, number 4, pages 221-231 (1995)).
Practitioners have taken several approaches to the treatment of dry eye. One common approach has been to supplement and stabilize the ocular tear film using so-called artificial tears instilled throughout the day. Other approaches include the use of ocular inserts that provide a tear substitute or stimulation of endogenous tear production.
Examples of the tear substitution approach include the use of buffered, isotonic saline solutions, aqueous solutions containing water soluble polymers that render the solutions more viscous and thus less easily shed by the eye. Tear reconstitution is also attempted by providing one or more components of the tear film such as phospholipids and oils. Phospholipid compositions have been shown to be useful in treating dry eye; see, e.g., McCulley and Shine, Tear film structure and dry eye, Contactologia, volume 20(4), pages 145-49 (1998); and Shine and McCulley, Keratoconjunctivitis sicca associated with meibomian secretion polar lipid abnormality, Archives of Ophthalmology, volume 116(7), pages 849-52 (1998). Examples of phospholipid compositions for the treatment of dry eye are disclosed in U.S. Pat. No. 4,131,651 (Shah et al.), U.S. Pat. No. 4,370,325 (Packman), U.S. Pat. No. 4,409,205 (Shively), U.S. Pat. No. 4,744,980 and U.S. Pat. No. 4,883,658 (Holly), U.S. Pat. No. 4,914,088 (Glonek), U.S. Pat. No. 5,075,104 (Gressel et al.), U.S. Pat. No. 5,278,151 (Korb et al.), U.S. Pat. No. 5,294,607 (Glonek et al.), U.S. Pat. No. 5,371,108 (Korb et al.) and U.S. Pat. No. 5,578,586 (Glonek et al.). U.S. Pat. No. 5,174,988 (Mautone et al.) discloses phospholipid drug delivery systems involving phospholipids, propellants and an active substance.
Another approach involves the provision of lubricating substances in lieu of artificial tears. For example, U.S. Pat. No. 4,818,537 (Guo) discloses the use of a lubricating, liposome-based composition, and U.S. Pat. No. 5,800,807 (Hu et al.) discloses compositions containing glycerin and propylene glycol for treating dry eye.
Although these approaches have met with some success, problems in the treatment of dry eye nevertheless remain. The use of tear substitutes, while temporarily effective, generally requires repeated application over the course of a patient's waking hours. It is not uncommon for a patient to have to apply artificial tear solution ten to twenty times over the course of the day. Such an undertaking is not only cumbersome and time consuming, but is also potentially very expensive. Transient symptoms of dry eye associated with refractive surgery have been reported to last in some cases from six weeks to six months or more following surgery.
Aside from efforts directed primarily to the alleviation of symptoms associated with dry eye, methods and compositions directed to treatment of the dry eye condition have also been pursued. For example, U.S. Pat. No. 5,041,434 (Lubkin) discloses the use of sex steroids, such as conjugated estrogens, to treat dry eye conditions in post-menopausal women; U.S. Pat. No. 5,290,572 (MacKeen) discloses the use of finely divided calcium ion compositions to stimulate pre-ocular tear film production; and U.S. Pat. No. 4,966,773 (Gressel et al.) discloses the use of microfine particles of one or more retinoids for ocular tissue normalization.
Some recent literature reports suggest that patients suffering from dry eye syndrome disproportionately exhibit the hallmarks of excessive inflammation in relevant ocular tissues, such as the lacrimal and meibomian glands. The use of various compounds to treat dry eye patients, such as steroids [e.g. U.S. Pat. No. 5,958,912; Marsh, et al., Topical nonpreserved methylprednisolone therapy for keratoconjunctivitis sicca in Sjogren syndrome, Ophthalmology, 106(4): 811-816 (1999); Pflugfelder, et. al. U.S. Pat. No. 6,153,607], cytokine release inhibitors (Yanni, J. M.; et. al. WO 0003705 A1), cyclosporine A [Tauber, J. Adv. Exp. Med. Biol. 1998, 438 (Lacrimal Gland, Tear Film, and Dry Eye Syndromes 2), 969], and 15-HETE (Yanni et. al., U.S. Pat. No. 5,696,166), has been disclosed.
The EgLN enzyme family are 2-oxoglutarate-dependent prolyl hydroxylases that catalyze the constitutive hydroxylation of the HIF-1α protein under normoxic conditions [Peso et al., J. Biol. Chem. 2003, 278(49), 48690-48695; Ivan et al., PNAS 2002, 99(21), 13459-13464]. The hydroxylated HIF-1α protein is targeted for polyubiquination and proteasomal degradation by pVHL, the protein product of the von Hippel-Landau gene. Under hypoxic conditions, oxygen concentration becomes rate-limiting and EgLN-catalyzed hydroxylation is inefficient. Consequently HIF-1α escapes destruction and forms a heterodimer with HIF-1β. The complex is transported to the nucleus, where it acts as a transcription factor to up-regulate production of hypoxia-induced proteins and growth factors, especially VEGF.
The EgLN-3 isozyme also appears to be involved as an effector of apoptosis in sympathetic neurons under certain conditions. In particular, EgLN-3 is a downstream effector of nerve growth factor (NGF) withdrawal-induced apoptosis in NGF-dependent neurons. Expression of SM-20, a rat ortholog of EgLN-3, increases after NGF withdrawal in sympathetic neurons [Lipscomb et al., J Neurochem. 1999, 73(1), 429-432]. Induced expression of SM-20 causes apoptosis in sympathetic neurons even in the presence of NGF in a caspase-dependent process [J Neurochem. 2003, 85(2), 318-328]. Although SM-20 is normally resident in the mitochondria, a truncated form that localizes to the cytoplasm due to loss of a mitochondrial targeting sequence still induces apoptosis [Lipscomb et al., J Biol Chem. 2001, 276(7), 5085-5092].
These findings have recently been extended to developing neurons [Lee et al., Cancer Cell 2005, 8, 155-167]. During embryogenesis, sympathetic neuronal precursor cells that fail to make synaptic connections are starved of NGF and undergo c-Jun-dependent apoptosis [Schlingensiepen et al., Cell Mol. Neurobiol. 1994, 14, 487-505]. The risk of a type of neuronal cancer called familial pheochromocytoma is increased by germline mutations that inactivate pVHL or NF1 (an antagonist of the NGF receptor TrkA), or that activate c-RET (the receptor for glial derived neurotrophic factor, which cross-talks with TrkA). In each of these cases the intracellular concentration of the c-Jun antagonist JunB increases, inhibiting apoptosis. Germline mutations that reduce the activity of succinate dehydrogenase (SDH) also increase familial pheochromocytoma risk. Succinate is a co-product of EgLN-3-catalyzed proline hydroxylation and feedback inhibits the enzyme, and thus needs to be removed by SDH for EgLN-3 prolyl hydroxylase activity. Sporadic pheochromocytoma due to somatic mutation in one of these genes is rare since apoptosis of “unconnected” sympathetic neuronal precursor cells is not important once embryogenesis is complete.
NGF withdrawal-induced apoptosis requires EgLN-3 proline hydroxylase activity. EgLN-3-induced cell death is not reduced by co-expression of JunB. Additionally, EgLN-3 expression knockdown by siRNA inhibits c-Jun induced cell death. These observations indicate that EgLN-3 is necessary and sufficient for NGF withdrawal-induced apoptosis, and acts downstream of c-Jun. The presumed protein target of EgLN-3-catalyzed proline hydroxylation that is important for apoptosis induction has not been identified, although it is suspected that pVHL's polyubiquination (and subsequent marking for proteasomal destruction) of a hyperphosphorylated form of atypical protein kinase C is responsible for pVHL's suppression of JunB.
Corneal nerves likely play a key role in maintaining homeostasis of the ocular surface by communicating with brain regarding required lacrimal gland support. In support of this theory, it has been observed that patients that undergo LASIK refractive surgery (where corneal nerves are severed) suffer from an increased incidence of dry eye [see for example: Ang, R. T.; Dartt, D. A.; Tsubota, K. Curr. Opin. Opthalmol. 2001, 12(4), 318-322]. Patients who suffer from dry eye have been reported to have aberrant corneal nerve morphology [Zhang et al., Cornea. 2005, 24(7), 818-824]. Mice deficient in the neurotrophic factor neurturin develop the characteristics of dry eye [Song et al., Invest. Opthalmol. Vis. Sci. 2003, 44(10), 4223-4229].
If corneal nerve dysfunction plays a role in dry eye disease pathology, then neurotrophic factors may represent a potential treatment [for a discussion, see: Pepose and Johnson, Am. J. Opthalmol. 2005, 139(6), 1090-1094]. Topical application of NGF has been reported to accelerate corneal innervation [Bazan and co-workers, Investigative Ophthalmology and Visual Science 2005, 46(9), 3121-3127; in this case the effect was synergistic in combination with the polyunsaturated fatty acid DHA] and enhance corneal sensitivity [Joo et al., Arch. Opthalmol. 2004, 122(9), 1338-1341] in rabbit models of refractive surgery, while treatment of dogs suffering from dry eye with topical NGF has been disclosed to improve tear quality, resolve corneal haze, and increase conjunctival goblet cell density [Coassin et al., Graefes Arch. Clin. Exp. Opthalmol. 2005, 243(2), 151-155].
The c-jun N-terminal kinase (JNK) pathway may play an important role in dry eye disease pathology. For example, JNK inhibition has been reported to reduce expression of IL-1β, TNF-α, and IL-8 induced by hyperosmolar stress in human limbal epithelial cells [Pflugfelder and co-workers, Exp. Eye Res. 2005, in press] and to increase tear production in a mouse model of dry eye [Zoukhri et al., J. Neurochem. 2006, 96(1), 126-135], and JNK inhibitors have been claimed for the treatment of dry eye (Gamache, US Published Patent Application, US 2004058875 A1).
The use of certain EgLN-3 enzyme inhibitors for the treatment of obesity (Fourney et al., U.S. Published Patent Application US2004/0235082A1), anemia via increasing endogenous erythropoietin production (Arend et al., U.S. Published Patent Application US2004/0254215A1), and fibrotic diseases (Weidmann et al., U.S. Pat. Nos. 6,093,730 and 5,719,164)), has been disclosed. Additionally, the use of certain EgLN-3 enzyme inhibitors has been disclosed for the postoperative treatment of glaucoma operations (ostensibly to maintain the filtration bleb) (Wiedmann et al., U.S. Pat. No. 6,020,350). However the use of the compounds of the present invention for the treatment of dry eye has not been disclosed.